The objective of this study is to determine nitric oxide (NO) production in normal pregnancy and preeclampsia. NO production is assessed from plasma levels and rates of urinary excretion of nitrate (a stable metabolite of NO) as well as blood level of NO-hemoglobin in gravid women. Similar measurements are obtained in women with preeclampsia and in women with transient gestational hypertension. A further objective of this study is to measure plasma TNF-alpha in normal gravid women, and in women with preeclampsia as well as transient, gestational hypertension, and evaluate if TNF-alpha relates to NO production.